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Calculate consumption OBD2

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  • Calculate consumption OBD2


    I am using The ELM327 in bluetooth to recover OBD II information in realtime.

    I would like to collect the consumption information.
    I know that this information is not directly readable but You can calculate it.

    For the gasoline vehicle: I use this calcul :

    MPG = (14.7 * 6.17 * 4.54 * VSS * 0.621371) / (3600 * MAF / 100)
    = 710.7 * VSS / MAF

    MPG - miles per gallon
    14.7 grams of air to 1 gram of gasoline - ideal air/fuel ratio
    6.17 pounds per gallon - density of gasoline (7.03 for diesel)
    4.54 grams per pound - conversion
    VSS - vehicle speed in kilometers per hour
    0.621371 miles per hour/kilometers per hour - conversion
    3600 seconds per hour - conversion
    MAF - mass air flow rate in 100 grams per second
    100 - to correct MAF to give grams per second

    And it's working !

    On the Diesel motorisation, I have modify the density of gasoline by the diesel constant.
    But it doesn't work the calculate consumption is very different from that displayed in my car (peugeot 207 diesel).

    Have you an idea to calculate consumption in diesel motor??

    Thank you

  • #2
    Julien, from my experience it is impossible to use MAF/MAP to calculate consumption on diesel vehicles.

    You can checkout hobdrive (, to see it's "EngineLoad" calculation method in action. As my users report, this (so far) is the most precise method for the diesel engines.
    Last edited by cail; 08-31-2011, 02:42 AM.